In recent years a number of dentifrices have been proposed for inhibiting the formation of calculus, or tartar as it is also referred to, on tooth surfaces. In particular, the patent literature contains numerous disclosures of dentifrices containing mixtures of various alkali metal pyrophosphate salts and soluble fluorides as anticalculus agents. Such disclosures appear, for example, in Parran et al U.S. Pat. Nos. 4,515,772, 4,590,066, 4,684,518, 4,806,339, 4,885,155 and 4,999,184; and in Gaffar et al U.S. Pat. Nos. 4,627,977, 4,806,340, 4,806,342, 4,869,898, 4,889,712, 4,906,456, 4,925654, 4,931,273 and 4,966,777.
More recently, in copending application Ser. No. 573,340 filed Aug. 30, 1991, entitled "Anticalculus Dentifrices" and owned by the assignee of the present invention, it has been disclosed that the addition of sodium bicarbonate to an alkali metal pyrophosphate/soluble fluoride-containing, anticalculus dentifrice imparts improved calculus-inhibiting properties thereto. The disclosure of that application is incorporated by reference herein.
It has been found that anticalculus toothpastes and gels and liquids incorporating both sodium bicarbonate and alkali metal pyrophosphate/soluble fluoride mixtures possess neat pH values (i.e., pH values of the toothpaste or gel prior to application and dilution with saliva) in the range of from about 9.0 to 9.6. Dentifrices which are so alkaline may be irritating to the oral mucosa. Accordingly, it is a principal object of the present invention to provide a buffering system for the sodium bicarbonate-alkali metal pyrophosphate/soluble fluoride anticalculus toothpastes or gels described in the aforesaid copending application. Other objects and advantages of the present invention will be apparent from the following description of preferred embodiments thereof.